Optimising the neutron environment of Radiation Portal Monitors

Lead Research Organisation: University of Sheffield
Department Name: Physics and Astronomy


Radiation portal monitors (RPMs) are currently installed at traffic choke points at ports and airports with little regard to their operating environment. Simple analyses suggest that the signal-to-noise ratio of the neutron components of these systems can be improved by judicious shielding, collimation and modifications of the environment, and that these can be done while improving throughput. This proposal will provide a detailed analysis, quantification and costing of these improvements. In addition to the threat neutron flux which the RPMs are intended to detect, there is a background flux of neutrons, predominantly the result of cosmic ray induced reactions in the atmosphere, in the ground below the detectors and also in adjacent infrastructure, in vehicles and their cargos. This background flux has quite a different directional distribution to the expected threat flux, so by shielding and collimation, it is possible to significantly reduce the background counts, improving the overall signal-to-noise ratio. This will result directly in a reduction of the minimum detectable amounts of threat material. Alternatively, the improved statistics can be used to make the same diagnosis in reduced time.

Planned Impact

This work will be of significant benefit to National Security through the implementation of enhanced performance of existing and future Radiation Portal Monitors whose primary purpose is to detect the presence of radioactive material and so prevent the free transportation of this throughout the world.b This has become a more pressing problem over the past decade due to the fall of thee Soviet Union and the increase in Global Terrorism.
Despite vast numbers of neutron sensitive RPMs being designed and installed, there are very few studies in the open literature of their response to the natural neutron environment. Those that have been published do not appear to be informed by any body of previous research and it thought probable that there is little additional classified research. The most detailed study available, by Frank*, is marred by incorrect cosmic ray neutron production mechanisms and spectra, uses completely unrealistic detector models and contains no attempt at experimental verification.
The collaborators in this proposal from the Universities of Glasgow and Sheffield as well as the Culham Centre for Fusion Energy have prior experience in the modelling and build of instrumentation for neutron generation, detection and experimental design that can contribute to all of the aspects of the work contained in this proposal. This project will build on that experience and lead to improved performance and throughput of current and future RPM installations.

* M.I. Frank. Improving neutron-based detection of fissile materials in the presence of cosmogenic neutron background.
PhD thesis, University of California, Berkeley, 2002. UMI Number 3063368


10 25 50
publication icon
McMillan, J.E. The production of wavelength shifting lightguides from clear acrylic sheet by disperse dyeing in Nuclear Instruments And Methods in Physics Research A

Description Portal radiation monitors used for security screening usually employ helium-3 tubes for neutron detection. The signal to noise ratio of neutron detection can be substantially improved at little cost by judicious application of shielding and collimation.
Exploitation Route Existing portals can be retrofitted with collimators and shielding. New designs can have these integrated.
Sectors Aerospace, Defence and Marine,Chemicals,Electronics,Energy,Environment,Security and Diplomacy,Transport

URL http://www.ccfe.ac.uk/assets/Documents/CCFE-PR(15)24.pdf
Description Sheffield Tour de France Small Artistic Commissions
Amount £1,580 (GBP)
Organisation Government of the UK 
Sector Public
Country United Kingdom
Start 03/2014 
End 04/2014
Description Collaboration with Corus/Tata Steel 
Organisation Tata Steel Europe
Country United Kingdom 
Sector Private 
PI Contribution Corus had a research division Corus-Redeem who were interested in radiation portal monitors for identifying radioactive materials in scrap steel feeds. We provided consultancy. One of their staff did a part time PhD on neutron detectors with us.
Collaborator Contribution Release of student one day per week.
Impact There are papers waiting for clearance. Tata Steel have reduced their research in the UK and are clearly far less interested in this than their predecessors.
Start Year 2006
Description Visit Mexborough Astronomical Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Around 80 people attended a meeting on "Radiation detection for screening of metal scrap and for international security"

Higher than usual turnout on a wet winter's evening
Year(s) Of Engagement Activity 2013